Add Xcode 4.5 to StandardCompilers map

We now have several reports of compiler versions for the GM,
e.g. Homebrew/homebrew#14944.

Library/Homebrew/macos.rb

@@ -189,7 +189,8 @@ module MacOS extend self
     "4.3.2" => {:llvm_build_version=>2336, :clang_version=>"3.1", :clang_build_version=>318},
     "4.3.3" => {:llvm_build_version=>2336, :clang_version=>"3.1", :clang_build_version=>318},
     "4.4" => {:llvm_build_version=>2336, :clang_version=>"4.0", :clang_build_version=>421},
-    "4.4.1" => {:llvm_build_version=>2336, :clang_version=>"4.0", :clang_build_version=>421}
+    "4.4.1" => {:llvm_build_version=>2336, :clang_version=>"4.0", :clang_build_version=>421},
+    "4.5" => {:llvm_build_version=>2336, :clang_version=>"4.1", :clang_build_version=>421}
   }
 
   def compilers_standard?